Dr. Oz Has Colon Cancer Scare

Dr. Mehmet Oz has always been outspoken about the importance of living a healthy lifestyle. So when the TV host, who boasts that he "always" takes his own advice, went in for a routine colonoscopy after his 50th birthday this year, he never imagined he'd have anything to worry about.

But during the examination, his doctor found an adenomatous polyp, or precancerous growth, inside his intestine, which if left behind, could have likely become colon cancer.

"This was a shakeup for me," Oz tells PEOPLE. "I have done everything right. I don't have any family history, and yet I'm high risk now."

The best-selling author and host of The Dr. Oz Show will have to be screened again in three months, then every five years after that.

"There's a lot of tension," he says. "It's frustrating. Why did this happen to me? It forces you to question the assumptions you make about life."

It has also forced him to find the upside of his potential health difficulty.

"The only thing holding me back from a terrible outcome is the dumb luck that I checked myself out for the show," says Oz, who will have to get regular colonoscopies to detect any new polyps. "I would have put this off, like a lot of people. But I bet this saved my life."

Oz will also discuss his health scare on The Dr. Oz Show's Sept. 7 season premiere.

For more on this story, pick up this week's issue of PEOPLE, on newsstands Friday